1. Field of the Invention
The present invention relates to an automatic paper feed apparatus, and particularly to an automatic paper feed apparatus having an improved paper separation device.
2. Description of Prior Art
An automatic paper feed apparatus generally includes a paper pickup roller for picking up one by one the paper sheets stored in a paper cassette from the uppermost one, and a paper feed roller for feeding the picked-up sheet into the automatic paper feed apparatus. The main concern for the automatic paper feed apparatus is how to automatically and reliably separate paper sheets one by one. Various conventional paper separation technologies have been proposed, within which utilizing the linear velocity difference between the paper pickup roller and the paper feed roller to accomplish the paper separation purpose is a cheap and reliable one.
Taiwan Patent No. 258086 discloses an automatic paper separation device in two embodiments. In the first embodiment, a driving member is employed to drive a one-way clutch to rotate. At the beginning of picking up one paper sheet, the one-way clutch drives a clearance bushing to rotate, which sequentially drives a paper pickup roller to rotate for paper pickup. When the paper sheet is further led to and moved by a paper feed roller, because the surface velocity of the paper feed roller is higher than that of the paper pickup roller, velocity will be transferred to the paper pickup roller through the paper sheet. Therefore, the surface velocity of the paper pickup roller is changed to be equal to that of the paper feed roller, and the rotation velocity of the paper pickup roller is thus higher than that of the clearance bushing. After the paper pickup roller rotates a predetermined angle, the clearance bushing is driven by the paper pickup roller to rotate, whereby the rotation velocity of the clearance bushing is changed to be higher than that of the one-way clutch. Consequently, the clearance bushing disengages from the one-way clutch to be in a standby condition. When the paper sheet leaves the paper pickup roller, the paper pickup roller will stop rotating because loss of driving power from the paper feed roller. The clearance bushing is then driven by the one-way clutch again, and drives the paper pickup roller again to pickup another paper sheet after rotating a predetermined angle. The feeding interval between the two sheets of paper is determined by the rotation angle of the clearance bushing during the above time period. The second embodiment is substantially the same as the first embodiment described above, except that a flat helical spring replaces the one-way clutch in the first embodiment.
As described above, the above conventional automatic paper feed device accomplishes the paper separation purpose by adopting a driving member to drive a one-way clutch, the one-way clutch driving a clearance bushing, and the clearance bushing driving the paper pickup roller in turn. However, such a combination complicates the manufacturing, increases the cost, and also occupies a large transverse space in an automatic paper feed apparatus.
Accordingly, to overcome the disadvantages as described above, an improved paper separation device for an automatic paper feed apparatus is desired.